1. Field of the Invention
The present invention relates to a passive keyless entry device also having a function for monitoring a tire pneumatic pressure by performing communication in both directions, and particularly, relates to a passive keyless entry device for monitoring the tire pneumatic pressure in which the tire pneumatic pressure can be stably monitored for a long time by performing the bidirectional communication and the entire construction is simplified by commonly using portions commonly usable in the passive keyless entry device and the tire pneumatic pressure monitoring device.
2. Description of the Related Art
There is conventionally a passive keyless entry (passive RKE) device for releasing a door lock and starting an engine by using a portable device from the exterior of an automobile as a device mounted to the automobile. Further, there is a tire pneumatic pressure monitoring device (TPMS) for periodically monitoring the pneumatic pressure of the tire by using a pneumatic pressure sensor mounted to each tire. In these devices, the main function of the passive keyless entry device is to release the door lock and start the engine, and the main function of the tire pneumatic pressure monitoring device is to monitor the pneumatic pressure of the tire. Accordingly, their functions are different from each other. Therefore, these devices are normally respectively mounted to the automobile as separate devices.
Here, FIG. 5 is a block diagram showing one example of the construction of a main portion of the already known passive keyless entry (passive RKE) device.
As shown in FIG. 5, this passive keyless entry device is constructed by a car mounting device 40 mounted to the automobile and a portable device 41 individually carried by a user, etc. In this case, the car mounting device 40 has a tuner section 42, a low frequency signal amplifying section (LF AMP) 43 and a controller 44. The tuner section 42 is connected to a high frequency wave receiving antenna 42(1) and converts a high frequency signal received by the high frequency wave receiving antenna 42(1) into a base band signal and outputs the base band signal. The low frequency signal amplifying section (LF AMP) 43 is connected to four low frequency wave transmitting antenna (down link antennas) 43(1), 43(2), 43(3), 43(4) individually arranged within the door handles of four doors of the automobile, and transmits a low frequency wireless signal in time division through each of the four low frequency wave transmitting antenna 43(1) to 43(4). The controller 44 controls the transmitting operation of the low frequency signal from the low frequency signal amplifying section 43 and also controls the operation of a car mounting control member such as a door lock mechanism 45, etc. in response to the supplied base band signal. The controller 44 is connected to the door lock mechanism 45 arranged in each door of the automobile, and an engine starting section 46 arranged in the vicinity of the engine.
This passive remote keyless entry device is schematically operated as follows.
The car mounting device 40 supplies a request signal in time division at a constant time interval from the low frequency signal amplifying section 43 to the four transmitting antennas 43(1) to 43(4) by the control of the controller 44. The low frequency wireless signal is transmitted from the corresponding transmitting antennas 43(1) to 43(4). At this time, when a user carrying the portable device 41 approaches the automobile and this portable device 41 receives the request signal transmitted from one of the low frequency wave transmitting antenna 43(1) to 43(4), e.g., the low frequency wave transmitting antenna 43(1), the portable device 41 forms an answer signal including an ID proper to this portable device 41 in response to the received request signal, and transmits the formed answer signal as a high frequency wireless signal. At this time, when the high frequency wave receiving antenna 42(1) receives this high frequency wireless signal on the car mounting device 40 side, the tuner section 42 receives and processes this high frequency wireless signal and converts the processed signal into a base band signal including the ID, and supplies the converted base band signal including the ID to the controller 44. When the base band signal including the ID is supplied to the controller 44, the controller 44 judges whether the supplied ID is conformed to one of IDs already registered or not. When the controller 44 judges that the supplied ID is conformed to the already registered ID, the controller 44 releases the operation of a car mounting control member according to the control contents instructed by the supplied base band signal, e.g., the door lock mechanism 45 of a door knob on the driver's seat side of the automobile. Thus, the user (driver) can open the driver's seat side door and can ride in the automobile by performing such control.
After such control is performed, the engine can be also subsequently started by setting the passive keyless entry device. When the passive keyless entry device is set in this way and the user (driver) rides in the automobile, communication using a wireless signal is performed between the car mounting device 40 and the portable device 41 carried by the user (driver). When the controller 44 confirms that the ID transmitted from the portable device 41 is the same ID as the ID of the portable device 41 judged just before by this communication, the controller 44 supplies a starting signal to the engine starting section 46 and makes the engine starting section 46 start the engine.
FIG. 6 is a block diagram showing one example of the construction of a main portion of the already known tire pneumatic pressure monitoring device (TPMS).
As shown in FIG. 6, this tire pneumatic pressure monitoring device is constructed by a TPMS receiver 50 arranged within the automobile, and TPMS transmitters (TPMS TX) 51(1), 51(2), 51(3), 51(4) individually mounted to four tires of the automobile. In this case, the TPMS receiver 50 has four high frequency wave receiving antennas 52(1), 52(2), 52(3), 52(4), a mixer section (MIX) 52, a TPMS tuner section 53, a signal intensity instructing section (RSSI) 54, a controller 55, a display section 56 and an alarm generating section 57. The four high frequency wave receiving antennas 52(1), 52(2), 52(3), 52(4) are arranged so as to correspond to the four TPMS transmitters 51(1), 51(2), 51(3), 51(4), and individually receive high frequency wireless signals transmitted from the corresponding TPMS transmitters 51(1) to 51(4). The mixer section 52 is connected to the four high frequency wave receiving antennas 52(1) to 52(4), and mixes and outputs the high frequency signals received by the four high frequency wave receiving antennas 52(1) to 52(4). The TPMS tuner section 53 receives the mixed high frequency signal and converts the mixed high frequency signal into a detecting signal showing the tire pneumatic pressure and outputs this detecting signal. The signal intensity instructing section 54 shows detecting signal intensity based on the detecting signal outputted from the TPMS tuner section 53. The controller 55 receives the detecting signal outputted from the TPMS tuner section 53 and the detecting signal intensity obtained by the signal intensity instructing section 54, and generates a tire pneumatic pressure measuring signal, an alarm signal showing a tire pneumatic pressure abnormality, etc. The display section 56 displays the tire pneumatic pressure measuring signal. The alarm generating section 57 generates an alarm when the alarm signal is supplied. A pressure sensor for detecting the tire pneumatic pressure is built in each of the TPMS transmitters 51(1), 51(2), 51(3), 51(4) although this pressure sensor is unillustrated.
This tire pneumatic pressure monitoring device (TPMS) is schematically operated as follows.
When a tire pneumatic pressure detecting time point allocated to the self transmitter has come, each of the four TPMS transmitters 51(1), 51(2), 51(3), 51(4) measures the pneumatic pressure of the corresponding tire by the built-in pressure sensor and transmits the measured tire pneumatic pressure measuring signal as a high frequency wireless signal. In this case, for example, the tire pneumatic pressure detecting time point is set to once for 30 minutes to one hour every each of the TPMS transmitters 51(1) to 51(4) at the stopping time (unusing time) of the automobile, and is also set to about once for one to three minutes at the running time (using time) of the automobile. The arriving time of the tire pneumatic pressure detecting time point is different every each of the four TPMS transmitters 51(1), 51(2), 51(3), 51(4), and the tire pneumatic pressure detecting time point comes in a sequential order in accordance with a determined period. When the tire pneumatic pressure detecting time point has come and the high frequency wave receiving antennas 52(1), 52(2), 52(3), 52(4) arranged correspondingly to the four TPMS transmitters 51(1), 51(2), 51(3), 51(4) sequentially receives this high frequency wireless signal on the TPMS receiver 50 side, the mixer section 52 mixes these received high frequency signals and converts these high frequency signals into a serial signal and supplies the converted serial signal to the TPMS tuner section 53. The TPMS tuner section 53 converts the supplied serial signal into a detecting signal showing the tire pneumatic pressure, and supplies the obtained detecting signal to the signal intensity instructing section 54 and the controller 55. The signal intensity instructing section 54 converts the supplied detecting signal into a detecting signal intensity showing its signal intensity, and supplies the converted detecting signal intensity to the controller 55. When the detecting signal and the detecting signal intensity are supplied to the controller 55, the controller 55 judges whether the supplied detecting signal intensity lies within the range of a prescribed intensity or not. When the controller 55 judges that this detecting signal intensity lies within the range of the prescribed intensity, the controller 55 makes the display section display the tire pneumatic pressure value shown by the detecting signal. In contrast to this, when the controller 55 judges that this detecting signal intensity does not lie within the range of the prescribed intensity, the controller 55 makes the display section display the tire pneumatic pressure value shown by the detecting signal and operates the alarm generating section 57 so as to inform the user (driver), etc. that the tire pneumatic pressure value has become abnormal. In this case, the alarm generated from the alarm generating section 57 may be set to ring a buzzer and turn on or off an alarm display lamp.
The above already known passive keyless entry device and the tire pneumatic pressure monitoring device were respectively recognized as devices for achieving separate independent functions. Therefore, when these devices are mounted to the automobile, these devices are mounted to suitable portions within the automobile every device.
Various car mounting devices are generally arranged within the automobile in addition to these devices. Therefore, a utilization space able to mount these devices is limited, and there is a case in which it is difficult to mount these devices to suitable portions within the automobile every each of these devices. Further, when these devices can be mounted to the automobile but are arranged in proximity to each other, these devices mutually utilize wireless signals so that the situation that their wireless signals interfere with each other and no exact control can be performed, is caused in a certain case.